The invention relates to a lift for raising and moving large cylindrical tanks, and more particularly to a four-wheel hand truck having a jack for raising a cylindrical tank and holding the tank off the floor while it is being moved, or placing the raised tank on a dolly or cart.
Large cylindrical tanks for industrial fluids, such as liquid nitrogen, have been extensively used for transporting such fluids from a storage plant to the user's premises. To minimize transportation costs per unit volume of fluid, the cylindrical tanks have become quite large, e.g., 23" in diameter and 52.5" high standing upright. Fixtures, namely valves and gauges on a domed upper end, are protected by a metal ring affixed to the domed upper end by at least two welded metal straps, each having a hole that serves as an eye to receive a hook from an overhead hoist at the storage plant.
Once filled with fluid, the cylindrical tank is delivered to the user's receiving dock. The problem then is for the user to move the tank to a location where the fluid is to be used over a period of days or weeks, and then move the empty tank back to the dock for return to the storage plant.
A two-wheel hand truck for moving such large cylindrical tanks is difficult and dangerous to use, particularly when the tank is full, due to the sheer size of the tank, and because of the large ratio of the tank height to the wheel base of the two-wheel hand truck. If the load on the hand truck starts to fall off to one side for any reason, the high center of gravity directly over the center of the wheel axle quickly shifts beyond the end of the axle. Once that occurs, the operator of the two-wheel hand truck is unable to stop the load from toppling. Righting the load on the hand truck is then virtually impossible, particularly if the tank is full of a fluid. To succeed in righting the load on the hand truck, it is usually necessary to unstrap the tank and then right it on the floor, after which it is again placed on the hand truck by tilting it forward, sliding a toe plate of the truck under it, and then, after strapping it back on the hand truck, tilting the hand truck rearwardly on its wheels.
A further problem with a large tank is placing it on a dolly or cart. A solution to this further problem is proposed in U.S. Pat. No. 4,536,123 which uses a jack to operate an assembly of linkages hinged at the corners to form two parallelograms that are joined to operate together. One side of each parallelogram is affixed to the main upright frame of the hand truck while the opposite side of the parallelogram is strapped to the tank at its upper end. A jack positioned between the upright main frame and the upper pair of parallel sides of the two joined parallelograms will pivot that upper pair of parallel sides upwardly, thereby raising the tank. A pair of forwardly diverging legs rigidly attached to the main upright frame near the bottom prevents it from tilting forward while the tank is being raised in this manner. Once raised, the tank is tilted rearwardly on the truck wheels in the usual manner in order to transport the tank to a desired location while balancing the weight on the two wheels of the truck. The tank thus raised is even more likely to topple to one side because the center of gravity has been raised. The pair of diverging legs will not assist in preventing this toppling because, while the hand truck is being operated to transport the tank, the legs remain off the floor.